Contact electrodes as used for reed switches consist in general, of a length of ferromagnetic wire which is flattened over a part of its length to form a flexible cantilever or blade.
Two of these electrodes are sealed into a glass tube with the blades overlapping within the tube. The overlapping ends are positioned to form a small gap which can be opened and closed by the action of an externally applied magnetic field.
It is desirable to make the gap between the blades as large as possible to enable the switch to handle high electrical power and to provide long operational life. For any one size of the contact electrodes the maximum gap between the blades is limited by magnetic saturation of the ferromagnetic material used. Also the separation between the blades cannot be increased too much by making the blades more flexible without upsetting the dynamic characteristics of the switch. If the blades are made too flexible the bounce time on closure may become prohibitively long. The duration of bounce depends primarily on the resonant frequency and the damping characteristics of the contacting blades.